Short telomeres are preferentially elongated by telomerase in human cells

Short telomeres have been shown to be preferentially elongated in both yeast and mouse models. We examined this in human cells, by utilising cells with large allelic telomere length differentials and observing the relative rates of elongation following the expression of hTERT. We observed that short telomeres are gradually elongated in the first 26 PDs of growth, whereas the longer telomeres displayed limited elongation in this period. Telomeres coalesced at similar lengths irrespective of their length prior to the expression of hTERT. These data indicate that short telomeres are marked for gradual elongation to a cell strain specific length threshold.     

Roosting behaviour is related to reproductive strategy in brood parasitic cowbirds

Shiny Cowbirds Molothrus bonariensis and Screaming Cowbirds Molothrus rufoaxillaris are closely related brood parasites but the former is socially polygynous or promiscuous and an extreme host generalist, whereas the latter is socially monogamous and parasitizes almost exclusively one host. Females of both species lay in relative darkness, before dawn, relying for host nest location on previous days’ prospecting activity, or possibly on following better‐informed roost associates. We studied the temporal and spatial patterns of roosting behaviour in these species to test the hypothesis that roosting behaviour of cowbirds is related to their breeding strategy (brood parasitism) and reflects differences in strategies between species. We recorded fidelity to a roost, location fidelity within a roost, inter‐individual spatial associations and timing of roost departures and parasitic events, using tagged individuals. Female Shiny Cowbirds and both sexes of Screaming Cowbirds showed marked fidelity in roosting location, and roost departures occurred both during and after the known time window for parasitism, with earlier departures probably corresponding to laying days. Screaming Cowbird females and males that were trapped together and showed high levels of association during the day, also showed high levels of association in the roost. We describe the spatial and temporal patterns of a relatively poorly known aspect of avian ecology in general and the behaviour of brood parasites in particular.     

Composition of a molluscan assemblage associated with macrophytes in Menzel Jemil (Bizerte lagoon,SW Mediterranean Sea)

The molluscan species composition and diversity associated with macrophytes was studied throughout 1 year at Menzel Jemil station (Bizerte lagoon, north‐west of Tunisia). A total of 7,539 individuals belonging to 13 species were collected. The molluscan assemblage was mainly composed of gastropods (98.12%, nine species), followed by bivalves (1.88%, four species). Hydrobia acuta ranked first with 49.97% of total abundance, followed by Bittium reticulatum (17.97%), Tritia mutabilis (11.38%), Haminoea navicula (8.98%), Phorcus articulatus (5.17%) and Cerithium vulgatum (3.94%). The large number of juvenile molluscs collected confirms the importance of macroalgae and seagrass for mollusc recruitment. Significant temporal variations of species richness, density and diversity indices of the mollusc assemblage have been observed during the year. Multivariate analyses applied to our data revealed significant relationships between the macrophyte composition and associated molluscan assemblage. The BIOENV analysis indicated that water temperature, phosphates concentration and macrophyte biomass were environmental variables most closely associated with the temporal variation of molluscan assemblage.     

西藏措勤地区早日垩世双壳类新材料

简述措勤地区双壳类的地层分布及组合特征,描述双壳类化石２０属２０种,其中有６新种。非海相双壳类（Ｉｓｏｄｏｍｅｌｌａ,Ｃｏｓｔｏｃｙｒｅｎａ）的发现具有重要意义。     

A trophic cascade in a diverse arthropod community caused by a generalist arthropod predator

We tested the hypothesis that a generalist arthropod predator, Tenodera sinensis Saussure, could trigger a trophic cascade in an old-field ecosystem. These mantids had relatively weak effects on abundance and biomass of other carnivorous arthropods as a group. The effect of mantids on herbivores was stronger than on carnivores, mainly concentrated in Homoptera and Diptera. Herbivore load was reduced by mantids with the consequence that overall plant biomass (mainly grasses) was increased. Percapita interaction strengths between mantids and other arthropod taxa were, for the most part, weakly negative. Our study demonstrates that a significant trophic cascade can be triggered by a generalist predator even within the framework of a diverse community with relatively diffuse interactions. Received: 13 January 1997 / Accepted: 28 July 1997     

Chloroplast assemblage by mechanical stimulation and its intercellular transmission in diatom cells

Summary By touching a cell ofPleurosira laevis, a centric diatom, the chloroplasts in the cortical cytoplasm immediately migrate to the nuclear cytoplasm which is located at the center of the cell. The time required for migration, is about 10 s and that for restoration is about 15 min. The touch could be replaced by an electric stimulation. A 7 V pulse for 1 ms was required for the induction of chloroplast assemblage. To obtain chloroplast assemblage in 50% of the cells, the amount of time and voltage required were inversely proportional. Higher concentrations of KCl also induced chloroplast assemblage. Neither contact nor electric stimulation in Ca²⁺ free medium induced chloroplast assemblage. Verapamil, a Ca²⁺ channel blocker, in medium suppressed the chloroplast assemblage. Ca²⁺ ionophore caused the chloroplast assemblage. These results suggested that the depolarization of the plasma membrane was a trigger of the induction of chloroplast assemblage and the influx of Ca²⁺ to the cytoplasm through the channel was essential for this. The chloroplast assemblage was transmitted successively to the other cells of the filamentous colony, though these cells were linked only by a mucilaginous substance. Furthermore, the transmission occurred in cells which were placed separately. The maximum distance possible for this jumping transmission was 200 m in the culture medium. To search for the release of any chemical transmitter, contact stimulation was applied to one cell at the middle of a filamentous colony which was placed in water streaming along the axis of the filament. Chloroplast assemblage was induced more in downstream cells than in upstream ones. This result suggested the existence of some substance which mediated the transmission of the stimulation.     

Eight decades of sampling reveal a contemporary novel fish assemblage in coastal nursery habitats

In order to adequately monitor biodiversity trends through time and their responses to natural or anthropogenic impacts, researchers require long time series that are often unavailable. This general lack of datasets that are several decades or longer makes establishing a background or baseline of diversity metrics difficult – especially when attempting to understand species composition changes against a backdrop of climate and ecological variability. Here, we present an analysis of a community of juvenile nearshore fishes based on nearly 8 decades of highly standardized Norwegian survey records. Using multivariate statistical techniques, we: (i) characterize the change in taxonomic community composition through time, (ii) determine whether there has been an increase in warm‐water affinity species relative to their cold water affinity counterparts, and (iii) characterize the temporal change in the species’ functional trait assemblage. Our results strongly indicate a shift toward a novel fish assemblage between the late 1990s and 2000s. The context of changes within the most recent two decades is in stark contrast to those during the 1960s and 1970s, but similar to those during the previous warm period during the 1930s and 1940s. This novel assemblage is tightly linked to the warming temperatures in the region portrayed by the increased presence of warm‐water species and a higher incidence of pelagic, planktivorous species. The results indicate a clear influence of ocean temperature on the region's juvenile fish community that points to climate‐mediated effects on the species assemblages of an important fish nursery area.     

MiR-103 regulates hepatocellular carcinoma growth by targeting AKAP12

AKAP12/Gravin (A kinase anchor protein 12) belongs to the group of A-kinase scaffold proteins and functions as a tumor suppressor in some human primary cancers. While AKAP12 is found consistently downregulated in hepatocellular carcinoma (HCC), its involvement in hepatocarcinogenesis has not been fully elucidated. We identified targeting sites for miR-103 in the 3′-untranslated region (3′-UTR) of AKAP12 by bioinformatic analysis and confirm their function by a luciferase reporter gene assay. We reveal miR-103 expression to be inversely correlated with AKAP12 in HCC tissue samples and show that overexpressed miR-103 promotes cell proliferation and inhibits apoptosis by downregulating AKAP12 expression in HCC cell lines. On the other hand, repression of miR-103 suppresses proliferation and promotes apoptosis in HCC cells by increasing AKAP12. In xenografted HCC tumors, overexpression of AKAP12 suppresses tumor growth whereas overexpression of miR-103 enhances tumor growth while repressing AKAP12. Since the activation of telomerase is crucial for cells to gain immortality and proliferation ability, we investigated whether AKAP12 expression affected telomerase activity in HCC cells. Both AKAP12 overexpression and protein kinase Cα (PKCα) inhibition prevent nuclear translocation and phosphorylation of TERT and reduce telomerase activity in HCC cells. These findings indicate that miR-103 potentially acts as an oncogene in HCC by inhibiting AKAP12 expression and raise the possibility that miR-103 increases telomerase activity by increasing PKCα activity. Thus, miR-103 may represent a new potential diagnostic and therapeutic target for HCC treatment.     

外周血单核细胞端粒长度和端粒酶hTERT 活性在心力衰竭中的变化研究

目的:探讨心力衰竭患者外周血单核细胞端粒长度和端粒酶h TERT活性在心衰发生进程中的变化情况和意义。方法:按照筛选要求选择患者,根据入选标准分为心衰组(49例)和非心衰组(44例)。记录患者的年龄、性别、生活习惯及疾病情况,超声检测患者心脏功能,测量左心室舒张末内径(LVEDD)、左心室射血分数(LVEF)。在不同时间点,抽取外周血分离单核细胞,用PCR方法检测端粒长度和端粒酶h TERT活性。结果:对照组比较,心衰组患者心脏左室舒张末内径明显增加,射血分数明显降低(P0.05);在第1、7天,心衰组患者外周血单核细胞端粒长度较对照组明显缩短、端粒酶h TERT活性明显增强。第7天较同组第1天端粒长度有所增加,端粒酶h TERT活性有所减低,但与对照组相比,端粒长度显著缩短,端粒酶h TERT显著增高(P0.05)。结论:心力衰竭后患者端粒长度和端粒酶h TERT活性明显变化,并随心衰发病具有一定波动,提示端粒和端粒酶可能参与了心衰发展进程。